Why can't I share files or printers over the Internet? (TCP ports 135, 139, 445 and 1025 are blocked)
FROM: SBC Internet Services
TO: SBC Internet Services Members
RE: All Applications, All Operating Systems, and All Domains
SUBJECT: Urgent Virus Alert
Dear SBC Internet Services Customer,
In response to a newly announced vulnerability attributed to computers running certain Microsoft Operating Systems, SBC Internet Services has blocked TCP ports 135, 139, 445 and 1025. These ports are known to be used by worms and viruses to spread to other computers through the Internet. Blocking these ports may affect your ability to use:
- Microsoft Outlook to access a Microsoft Exchange server over the Internet
- File sharing over the Internet
- Print sharing over the Internet
This action should not affect the vast majority of our members, and does not affect using Microsoft Outlook or other email programs over a local area network.
The block is scheduled to begin on Thursday, April 29, 2004. Beginning at that time, you may notice that you are unable to continue the above activities over the Internet. Other uses of your Internet Access service will not be affected.
How long will this port blocking last?
With the cooperation of subscribers, and the use of anti-virus software and
firewalls, we hope to have this issue contained in a relatively short period
of time.
Are there any workarounds?
You may be able to work around port blocking. Some workarounds you may want
to investigate include:
- Using Microsoft Outlook Web Access
- Using Microsoft point-to-point tunneling
- Using a Virtual Private Network (VPN)
You may need assistance from a networking professional to set up these workarounds.
Will anything else be affected?
Other computer applications may use ports 135, 139, 445 and 1025, although
they are mostly used for the purposes outlined above.
Why are you doing this now?
As the result of a growing number of apparent security vulnerabilities, SBC
Internet Services is blocking ports in an effort to protect our networks and
the security of our customers’ computers.
Because SBC Internet Services conducts security checks on its network,
do members need to be concerned about additional Internet Security measures?
Yes, members should realize they are responsible for the security of their
own computers. Our network security scans and port blocking are not a substitute
for protecting and patching your own computers. We recommend use of personal
hardware and/or software firewalls, and we suggest that all members install
anti-virus software to scan the contents of their computers for viruses and
worms.
Sincerely,
SBC Internet Services
Copyright © 2003 SBC Internet Services. All rights reserved.